Hi, I can't comment on the comparative difficulty, but I can comment on the two possible paths to the Acropolis. We visited Greece in June, and we ascended both trails. I have a heart condition, and therefore cannot climb stairs or steep hills quickly. I have to take a lot of breaks on the way up.
The trail that starts closer to the Acropolis museum is more of a slanted trail (think: going for a hike). It has dirt and small rocks underfoot along with some uneven stone steps. There are multiple places to pause on the way up. It seemed to be longer than the other trail, but that could just be my perception. Toward the top, it meets up with the main trail.
The trail by the main entrance closer to the Forum has more steps. The steps are made of stone and have been placed there. Kind of like someone's patio if it had steps. That being said, they are still bumpy and not completely even. This trail seemed to be shorter but increased in altitude more quickly. I found it harder to walk up this trail because of the quicker ascent by steps, but that was due to my heart condition.
At the top, you will have some large stones to navigate your way up. Be sure to wear shoes that have good grip! If you can take your time, it should be very do-able. Take a look at both trails. Maybe one will suit your situation more than the other. Have a great time! We really enjoyed Athens and the rest of Greece!